Main menu

Post navigation

Those Mercedes wheel rims… an update

The Mercedes wheel rim and apparent wheel nut.
Image used with kind permission of XPB.CC

I’ve just been shown the FIA regulations regarding wheel rims and they make for interesting reading.

Here they are:

12.8.1 The only parts which may be physically attached to the wheel in addition to the tyre are surface treatments for appearance and protection, valves for filling and discharging the tyre, balance weights, drive pegs, tyre pressure and temperature monitoring devices and spacers on the inboard mounting face of identical specification on all wheels for the same axle.

12.8.2 The wheel must be attached to the car with a single fastener. The outer diameter of the fastener must not exceed 105mm and the axial length must not exceed 75mm. The wheel fastener may not attach or mount any part to the car except the wheel assembly described in Article 12.8.1.

What is interesting is that wheel fasteners / wheel nuts are not included in the list in 12.8.1 of things that are allowed to be attached to the wheel assembly / rim. And yet in Article 12.8.2 it states that a wheel fastener may not be attached to any part of the car other than those very same wheel assemblies.

So what does this mean?

Right now, not a lot as I don’t have clarification yet from Mercedes of what I saw. Similarly, we have no idea if what I saw will be or was ever intended to be raced.

It was pitstop practice. Just like in a practice match of soccer, you can play 16 men and use your hands if you really want to, so in a pitstop practice the team doesn’t have to use the very same devices it will use in race conditions.

But from the way the regulations are worded, could there be space for a loophole? And if so, could this be something Mercedes are thinking about exploiting? Because from the image above, it certainly looks that way.

Look at 12.8.1 this way: The wheel rim and tyre are sitting in the pit garage. Screwed on to the rim are 3 spinners, a clock and a pyrometer. However, just prior to the installation of said rim and tyre to the car, all those things are removed, the wheel is mounted and all is legal.

Back to the wheel nut. The wheel nut is attached to the rim prior to installation on the car. However, when all is said and done the wheel nut is exactly where it is supposed to be; attached to the hub thereby mounting the wheel to the car in a 100% legal manner.

One last analogy, you’re not allowed to leave the wheel nut gun attached to the wheel when the car leaves the pit, but the gun is attached to the wheel just before the car is released.

It’s not attached. It rotates freely within the central tube of the wheel i.e. there is a small but distinct gap between the rim and the nut assemblies. It may be co-located, or captive, or restrained or some such other term to describe it being seated there, maybe using a collar or detent, but it’s not technically attached to the rim. If you think about what it has to functionally do, it can’t be. And that’s the loophole.